Responder.java

// my motivation to use enum is so you dont need to create new objects everytime a command is executed
// instead you simply call a static method. and to iterate through a list of static methods we use enums.

// So this is a typical enum u encounter all the time
enum MyEnum {
  A, B, C;
}
// However enums are capable of having properties and methods!
// if u define a method in an enum all enums will have it
// e.g.
enum MyEnum {
  A,B,C;
  public void func() {
    System.out.println("hi");
  }
} 
//      MyEnum.A.func() prints 'hi'
//      MyEnum.B.func() prints 'hi'
//      MyEnum.C.func() prints 'hi'
// and if u want properties for each enum you can give it arguments in the constructor
// yes enums have constructors, normally java provides a default constructor but you can implement your own!
//e.g. 
enum MyEnum {
  A(1), B(2), C(3);
  private int num;
  MyEmum(int i) {
    num = i;
  }
  public int func() {
    System.out.println(num);
    return num * 5;
  }
}
//     MyEnum.A.func() will print '1' and return 5
//     MyEnum.B.func() will print '2' and return 10
//     MyEnum.C.func() will print '3' and return 15

// so in our case our enums (Responses.java) has a property regex and a
// ResponseFunc which can be a lambda or instance that implements ResponseFunc interface
// it also has a call function which checks if an input string matches regex then uses input
// and state as arguments for the ResponseFunc lambda or instance
// so lets say i have a state and input i can process it like so:
State s = new State();
String input = "create deck german-deck";
Responses.BYE.call(input, s);
Responses.CREATECARD.call(input,s);
Responses.CREATEDECK.call(input,s);
// and so on...
// but instead of calling one by one we can use a for loop iterating all enums
for (Responses r : Responses.values()) {
  r.call(input,s);
}
// now the code will check every enum even after a successful match.
// to exit the loop on success the call has to return a boolean indicating success
// so finally read the following and see if it makes sense:
// (be warned all of this is written on my phone and not checked by an ide to be valid java code)

public class Responder {

  public static State takeInput(String input, State state) {
    for (Responses r : Responses.values()) {
      if (r.call(input, state)) {
        break;
      }
    }
  }
}

enum Responses {
  COMMAND1("com1regex", (i,s) -> {
    System.out.println("your input matches com1regex");
    return true;
  });
  
  private String regex;
  private ResponseFunc func;

  Response(String r, ResponseFunc f) {
      regex = r;
      func = f;
  }
  
  public boolean call(String i, State s) {
      if (i.matches(regex)) {
          return func.funcCall(i, s);
      }
      return false;
  }
}